With improvements in recording-reproduction methods, magnetic heads, magnetic recording media, etc. for use in magnetic recording systems, rapid advances have been made in the field of magnetic recording techniques in recent years for magnetic recording with an increased density.
To provide improved magnetic recording media for high-density recording, efforts have been made chiefly to give an increased coercive force (Hc) or increased residual magnetic flux density (Br) to the magnetic film and to reduce the thickness of the medium to the greatest possible extent. For example, in the case of hard discs for use in Winchester recording systems wherein the head and disc are sealed off, coating-type recording media which comprise a magnetic film composed of a highly magnetic powder and an organic binder and formed on a nonmagnetic substrate have been changed over to media of the thin metal film which comprise a magnetic film in the form of a thin metal film and having higher magnetic characteristics for high-density recording.
The magnetic recording medium of the thin metal film is prepared by coating an aluminum alloy or like nonmagnetic substrate with a film having a specified thickness of an iron family element, alloy of such elements, or an alloy composed of an iron family element or alloy of such elements and an element other than the iron family elements by vacuum evaporation, sputtering, ion-beam deposition or like method. The composition of the thin metal film is selectively determined in view of the desired magnetic properties, recording-reproduction characteristics, durability (chiefly weather resistance), etc. as evaluated collectively. Generally, Co, Co--Ni alloy or Co--Fe alloy is primarily used.
The magnetic recording media of the thin metal film prepared using such a material possess excellent magnetic characteristics for high-density recording but are not always satisfactory in noise characteristics. Accordingly it has been desired to provide a magnetic recording medium which is amenable to high-density recording and outstanding in noise characteristics.